This will not be much of a review, because I do not actually own a Dell XPS 13. I have only a Dell XPS 13 with Fedora 18 booted from a Live USB image, but my short experience is worth mentioning.
In order to boot from the USB drive, I had to turn off Secure Boot in the BIOS. Once Secure Boot was off, I was able to get to the traditional boot menu and boot from the USB drive to Live Fedora 18
Once logged in everything felt very snappy. I was able to connect to my wireless network without a problem.
The new 1080p screen is absolutely gorgeous. The function keys to control brightness and volume appeared to work well, but I do not recall if the keyboard backlight brightness keys worked.
The only thing that did not fully work was the touchpad.
The Dell XPS 13 uses a Cypress Touchpad, but Live Fedora 18 recognizes it as ImPS/2 Generic Wheel Mouse. This allows basic touchpad functionality, but tap-to-click and two-finger scrolling did not work.
However, it looks like Dell and Canonical have backported a fix, and the touchpad is properly recognized in Linux kernel 3.8.23-203.